Membranoproliferative Glomerulonephritis Associated with Chronic Lymphocytic Leukemia Treated with Obinutuzumab

Introduction: Chronic lymphocytic leukemia (CLL) is a B-cell malignancy primarily affecting older adults. Kidney involvement is underrecognized and usually reported in case studies, with manifestations ranging from interstitial infiltration to glomerulopathies and drug-related nephrotoxicity. Among glomerular lesions, membranoproliferative glomerulonephritis (MPGN) is one of the most frequently described. Case Description: We report a 71-year-old man with CLL diagnosed in 2017, with no current treatment. At routine follow-up, proteinuria and renal dysfunction were identified. He was asymptomatic except for mild peripheral edema. Laboratory tests showed elevated creatinine and urea, anemia, thrombocytopenia, and lymphocytic leukocytosis. Urinalysis revealed 3+ proteinuria, hematuria, and 2.8 g/day proteinuria. Serologies, complement levels, and immunologic tests were unremarkable. Kidney biopsy revealed MPGN, showing mesangial hypercellularity, segmental endocapillary proliferation, and pseudothrombus-like subendothelial deposits. Immunofluorescence showed isolated mesangial C3 staining. Treatment with venetoclax and monthly obinutuzumab (1 g for 6 months) was initiated. After the first dose, the patient developed tumor lysis syndrome with acute kidney injury, managed conservatively. He completed therapy without major adverse events. Following treatment, leukocyte counts normalized, renal function improved, and proteinuria dropped to <100 mg/day. Discussion: Treatment of MPGN in CLL typically targets the underlying malignancy. Previous reports describe responses to chlorambucil, cyclophosphamide, and rituximab. To our knowledge, this is the first reported case of CLL-associated MPGN treated with obinutuzumab. Obinutuzumab is a humanized anti-CD20 monoclonal antibody approved for first-line treatment of CLL, often combined with venetoclax. It induces stronger immune-mediated cytotoxicity than rituximab. Nie et al. studied 7 cases of CLL with renal involvement, with nearly 50% showing leukemic infiltration and only one case of MPGN. Javaugue et al. reported 11 patients with CLL and renal disease; in five cases, it was directly related to CLL, all presenting glomerular involvement. All received clone-targeted therapy. This case highlights the potential of obinutuzumab as an effective treatment for glomerular disease in patients with CLL.